September weather forecast
Key Largo, FL

A clear seascape and cloudy evening sky in Key Largo, Florida
A clear seascape and cloudy evening sky in Key Largo, Florida

Weather in September

The first month of the autumn, September, is also a moderately hot month in Key Largo, Florida, with temperature in the range of an average high of 84.6°F (29.2°C) and an average low of 81.7°F (27.6°C).

Temperature

In Key Largo, the average high-temperature in September is relatively the same as in August - a still warm 84.6°F (29.2°C). In Key Largo, the average low-temperature is 81.7°F (27.6°C).

Heat index

The average heat index in September is estimated at a tropical 93.2°F (34°C). Take extra precautions, as heat cramps and heat exhaustion are possible. Sustained activity may result in heatstroke.
Note that heat index values are valued for light wind and location in the shade. With exposure to direct sunlight, the heat index may be increased by up to 15 Fahrenheit (8 Celsius) degrees.
Note: The heat index, also known as 'felt air temperature', 'apparent temperature', 'real feel', or 'feels like', is a calculated temperature value of how hot it feels when the moisture in the air is factored in. This effect is subjective, depending on the activity and individual's heat perception influenced by various reasons (wind, clothing, pregnancy). Bear in mind that direct sunshine exposure increases weather impact, and may raise heat index by up to 15 Fahrenheit (8 Celsius) degrees. Heat index values are particularly important for children. Young children are generally more endangered than adults, as they usually less sweat. And also, due to larger skin surface relative to their small bodies and higher heat production as a result of their activity.

Humidity

In Key Largo, the average relative humidity in September is 74%.

Rainfall

In Key Largo, during September, the rain falls for 22.9 days and regularly aggregates up to 4.25" (108mm) of precipitation. In Key Largo, during the entire year, the rain falls for 190.1 days and collects up to 27.05" (687mm) of precipitation.

Ocean temperature

In Key Largo, the average seawater temperature in September is 85.6°F (29.8°C).
Note: Water temperature between 77°F (25°C) and 84.2°F (29°C) is regarded as very warm and enjoyable by all. With these temperatures, water activities are pleasurable, without feeling uncomfortable for prolonged periods.

Daylight

In Key Largo, the average length of the day in September is 12h and 17min.
On the first day of the month, sunrise is at 7:02 am and sunset at 7:41 pm. On the last day of September, in Key Largo, Florida, sunrise is at 7:13 am and sunset at 7:10 pm EDT.

Sunshine

In September, the average sunshine in Key Largo is 9h.

UV index

The months with the highest UV index in Key Largo are April through October, with an average maximum UV index of 7. A UV Index value of 6 to 7 symbolizes a high threat to health from unsafe exposure to UV radiation for ordinary individuals.
Note: In September, the average maximum UV index of 7 translate into the following recommendations:
Take precautions and adopt sun safety practices. Protection against sunburn is obliged. Seek shade and minimize exposure to direct Sun in a period between 10 a.m. and 4 p.m. when UV radiation is most intense; keep in mind that shade structures like parasols or canopies do not provide perfect sun protection. On bright days sunglasses that block both UVA and UVB rays should be worn. A hat with a wide brim is extremely helpful, as it can prevent roughly 50% of UV radiation from reaching the eyes. Caution! The reflection of sand and water significantly increases the intensity of the Sun's UV radiation.
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FAQ

What is the temperature in September in Key Largo?

In September, the average high-temperature is 84.6°F (29.2°C), and the average low-temperature is 81.7°F (27.6°C). in September, the average heat index (a.k.a. 'apparent temperature', 'feels like'), which takes the relative humidity and factors it into the air temperature reading, is estimated at 93.2°F (34°C).

What is the average humidity in September in Key Largo?

In Key Largo, Florida, the average relative humidity in September is 74%.

How many days does it rain in September in Key Largo?

In Key Largo, during September, the rain falls for 22.9 days and regularly aggregates up to 4.25" (108mm) of precipitation.

What is the water temperature in September in Key Largo?

In Key Largo, Florida, in September, the average water temperature is 85.6°F (29.8°C). For any water activity, surface water temperatures between 77°F (25°C) and 84.2°F (29°C) are considered as excellent and extremely pleasant for lengthened periods.

What is the average length of the day in September in Key Largo?

In September, the average day length in Key Largo is 12h and 17min.

When are sunrise and sunset in September in Key Largo?

On the first day of September, sunrise is at 7:02 am and sunset at 7:41 pm. On the last day of the month, sunrise is at 7:13 am and sunset at 7:10 pm EDT.

How long on average sun shines in September in Key Largo?

The average sunshine duration in September is 9h.

What is the month with the highest UV index in Key Largo?

April through October, with an average maximum UV index of 7, are months with the highest UV index in Key Largo.

What is the UV index reading in September in Key Largo?

In September, the average daily maximum UV index in Key Largo, Florida, is 7. A UV Index of 6 to 7 symbolizes a high health risk from unsafe exposure to Sun's UV rays.

Average temperature in September
Key Largo, FL

Average temperature in September - Key Largo, FL
  • Average high temperature in September: 84.6°F

The warmest month (with the highest average high temperature) is August (85.5°F).
The month with the lowest average high temperature is January (72.7°F).

  • Average low temperature in September: 81.7°F

The month with the highest average low temperature is August (82.9°F).
The coldest month (with the lowest average low temperature) is January (66.9°F).

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Average pressure in September
Key Largo, FL

Average pressure in September - Key Largo, FL
  • Average pressure in September: 29.94"Hg

The month with the highest atmospheric pressure is January (30.1"Hg).
The months with the lowest atmospheric pressure are September and October (29.94"Hg).

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Average wind speed in September
Key Largo, FL

Average wind speed in September - Key Largo, FL
  • Average wind speed in September: 9.4mph

The windiest month (with the highest average wind speed) is January (12.9mph).
The calmest month (with the lowest average wind speed) is July (8.9mph).

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Average humidity in September
Key Largo, FL

Average humidity in September - Key Largo, FL
  • Average humidity in September: 74%

The months with the highest relative humidity are February, June and December (76%).
The month with the lowest relative humidity is March (73%).

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Average rainfall in September
Key Largo, FL

Average rainfall in September - Key Largo, FL
  • Average rainfall in September: 4.25"

The wettest month (with the highest rainfall) is August (4.33").
The driest month (with the least rainfall) is March (0.59").

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Average rainfall days in September
Key Largo, FL

Average rainfall days in September - Key Largo, FL
  • Average rainfall days in September: 22.9 days

The month with the highest number of rainy days is September (22.9 days).
The month with the least rainy days is February (9.7 days).

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Average sea temperature in September
Key Largo, FL

Average sea temperature in September - Key Largo, FL
  • Average sea temperature in September: 85.5°F

The best month for swimming (with the highest average sea temperature) is August (86.5°F).
The coldest month (with the lowest average sea temperature) is February (74°F).

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Average daylight in September /
Average sunshine in September
Key Largo, FL

Average daylight in September / Average sunshine in September - Key Largo, FL
  • Average daylight in September: 12h and 17min

The month with the longest days is June (Average daylight: 13h and 40min).
The month with the shortest days is December (Average daylight: 10h and 37min).

  • Average sunshine in September: 9h and 0min

The month with the most sunshine is July (Average sunshine: 11h and 0min).
The month with the least sunshine is December (Average sunshine: 6h and 24min).

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Average sunshine days in September
Key Largo, FL

Average sunshine days in September - Key Largo, FL
  • Average sunshine days in September: 5.2 days

The month with the most sunshine days is January (17.3 days).
The month with the least sunshine days is September (5.2 days).

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Average UV index in September
Key Largo, FL

Average UV index in September - Key Largo, FL
  • Average UV index in September: 7

The months with the highest UV index are April, May, June, July, August, September and October (UV index 7).
The month with the lowest UV index is January (UV index 5).

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Average cloud cover in September
Key Largo, FL

Average cloud cover in September - Key Largo, FL
  • Average cloud cover in September: 30

The month with the most cloud cover is October (Cloud cover 35).
The month with the least cloud cover is April (Cloud cover 26).

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Average visibility in September
Key Largo, FL

Average visibility in September - Key Largo, FL
  • Average visibility in September: 6mi

The months with the highest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).
The months with the lowest visibility are January, February, March, April, May, June, July, August, September, October, November and December (6mi).

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